This invention relates to coil bobbins and to methods of manufacturing electrical coils. The invention is herein disclosed with particular reference to the manufacture of relatively small coils having fine wire windings provided with varnish-type insulation however, the principles of the invention are applicable to other types of electrical coils.
It has been common practice in the past in the manufacture of electrical coils to provide metal terminals in the flanges of the coil bobbin and, during winding of the coils, the wire is wrapped around one of the terminal posts, led to the coil supporting surface, and wound on the supporting surface of the bobbin until the coil contains the required number of turns. After winding, the coil wire is wrapped around the remaining post and wire is cut or severed. Thereafter, ends of the coil wire are soldered to the terminal post by simply dipping the posts into a solder bath.
During the past few years, a trend has developed towards the use of contact terminals for coils which do not require soldering but which penetrate the insulation of the coil wire and establish electrical contact with the core thereof. U.S. Pat. Nos. 4,026,013 and 3,979,615 show two types of contact terminals which are being used in the electrical industry for establishing contact with electrical coils. In accordance with the principles of these prior art patents, cavities are provided in the coil support which are dimensioned to receive the terminals and the coil wire is located in these cavities during the winding process. After the winding process has been completed, it is merely necessary to insert terminals into the cavities to establish contact with the ends of the wire. The above identified U.S. patents do not require separate terminal posts on the bobbin as explained above with reference to the commonly known soldering technique for electrical coil wires.
Many of the coil winding processes which are presently being practiced in the electrical industry are carried out by automatic and semi-automatic coil winding machines and these coil winding machines were developed specifically for coil bobbins having terminal posts extending therefrom. Coil winding machines are available which are capable of carrying out all of the operations discussed above, that is, of wrapping the wire around one terminal post, winding the wire around the coil supporting surface, and then wrapping the wire around the remaining terminal post. These coil winding machines are, therefore, not always compatible with the solderless coil wire terminating techniques disclosed in the above identified U.S. Pat. Nos. 4,026,013 and 3,979,615. There is a very large investment in existing coil winding machinery and for this reason it would be uneconomical and impractical for coil manufacturers to convert from solder terminating techniques to the solderless termination processes disclosed in the above identified patents.
The instant invention is directed to the achievement of solderless terminations of coil wires by methods which are fully compatible with coil winding machines of the types which are presently being used in the coil winding industry for solder type terminations. In general, the objects of the invention are achieved by providing a bobbin which has wire binding posts extending therefrom as part of the bobbin molding. The coil bobbin also has terminal receiving cavities in one of its flanges which are located such that the operations of wrapping the coil wire around the first binding post, passing the coil wire through one of the cavities, winding the required number of turns on the coil supporting surface, passing the wire through the second cavity and finally wrapping the wire around the remaining post, can be carried out by a coil winding machine. After these operations have been carried out, terminals can be inserted into the cavities and the binding posts can be cut from the bobbin. Cutting of the binding post also results in cutting of the coil wire adjacent to the fixed ends of the binding posts. The completed bobbin thus contains terminals in its terminal receiving cavities which are connected to the coil wire and which can be connected to the external conductors when the coil is placed in a circuit.
It is accordingly an object of the invention to provide an improved coil support such as a coil bobbin. A further object is to provide improved methods for the manufacture of electrical coils. A further object is the achievement of solderless electrical coils by manufacturing methods which are compatible with a variety of known types of coil winding equipment.